arXiv subjects

Atsushi Hosaka

Publications and source records attributed to Atsushi Hosaka.

At least 37 records · Page 2Linked to original sources

arXiv2023

Production of the $ΞN$ dibaryon as a weakly bound system in $pp$ collisions

The $ΞN$ interaction plays an important role in our understanding on the long-anticipated $H$-dibaryon. Recent lattice QCD calculations verified the attractive nature of the $ΞN$ interaction. On the other hand, whether it is strong enough to generate a bound state remains inconclusive.In this work, assuming that it can generate a weakly bound state, we study the yields of the $ΞN$ dibaryon for different binding energies in $pp$ collisions at 7 TeV using the coalescence model and the transport model PACIAE. The yields are estimated first numerically and then analytically adopting a Yukawa-type wave function. In particular, we find that in the weak binding limit, there exists a universal relation between the yield and the binding energy, valid for $pp$ collisions.

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arXiv2023

Fully-strange tetraquark states with the exotic quantum numbers $J^{PC} = 0^{+-}$ and $2^{+-}$

We study the fully-strange tetraquark states with the exotic quantum numbers $J^{PC} = 0^{+-}$ and $2^{+-}$. We construct their corresponding diquark-antidiquark interpolating currents, and apply the QCD sum rule method to calculate both their diagonal and off-diagonal correlation functions. The obtained results are used to construct some mixing currents that are nearly non-correlated, from which we extract the masses of the lowest-lying states to be $M_{0^{+-}} = 2.45^{+0.33}_{-0.44}$ GeV and $M_{2^{+-}} = 3.07^{+0.25}_{-0.33}$ GeV. We apply the Fierz rearrangement to transform the diquark-antidiquark currents to be the combinations of meson-meson currents, and the obtained Fierz identities indicate that these two states may be searched for in the $P$-wave $ϕ(1020) f_0(1710)/ϕ(1020) f_2^\prime(1525) (\to ϕK \bar K / ϕππ)$ channels.

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arXiv2023

Doubly heavy tetraquarks including one-pion exchange potential

Spectrum of the doubly heavy tetraquarks is studied in a constituent quark model including one-pion exchange (OPE) potential. Central and tensor forces induced by OPE between two light quarks are considered. Our results show that $I(J^P)=0(1^+)$ compact bound states are shifted up because of the repulsive central force between $\bar{q}\bar{q}$. This effect possibly leads to the small binding energy in $T_{cc}$. In addition, a $I(J^P)=1(1^+)$ resonant state is reported with $ E=10641 \ \rm{MeV},Γ=15 \ \rm{MeV}$ and $ E=10640 \ \rm{MeV},Γ=15 \ \rm{MeV}$, without and with including OPE potential, respectively. The repulsive central force and attractive tensor force almost cancel with each other and leave a small energy difference when OPE potential is included.

nucl-th↗

arXiv2023

Axial anomaly effect on three-quark and five-quark singly heavy baryons

Effects of the $U(1)_A$ axial anomaly on the mass spectrum of singly heavy baryons (SHBs) is studied in terms of the chiral effective theory based on the chiral linear representation for light flavors. We consider SHBs made of both three quarks ($Qqq$) and five quarks ($Qqqq\bar{q}$). For the three-quark SHBs we prove that the inverse mass hierarchy for the negative-parity $Λ_c$ and $Ξ_c$ is realized only when the $U(1)_A$ anomaly is present. For the five-quark SHBs, in contrast, it is found that the $U(1)_A$ anomaly does not change the mass spectrum at the leading order, and accordingly their decay properties induced by emitting a pseudoscalar meson are not affected by the anomaly. Moreover, taking into account small mixings between the three-quark and five-quark SHBs, we find that the observed $Ξ_c$ excited state, either $Ξ_c(2923)$ or $Ξ_c(2930)$, can be consistently regarded as a negative-parity SHB that is dominated by the five-quark component. We also predict a new negative-parity five-quark dominant $Λ_c$, whose mass is around $2700$ MeV and the decay width is of order a few MeV, which provides useful information for future experiments to check our description.

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arXiv2023

Understanding the nature of $Ω(2012)$ in a coupled-channel approach

We perform a systematic analysis of the mass and strong decays of the $Ω(2012)$ resonance in a coupled-channel approach of a bare three-quark state and a composite meson-baryon state. Besides the coupling of the bare state and $Ξ^* \bar K$ channel, the effective meson-baryon interactions are also included. We find a pole with mass of $2008$ MeV by solving the Bethe-Salpeter equation. The calculated decay widths and its ratios of branching fractions $\mathcal {R}_{Ξ\bar K}^{Ξπ\bar K}$ agree well with the new experimental measurement by Belle Collaboration. Our results suggest that both three-quark core and $Ξ^* \bar K$ channel are essential for the description of the $Ω(2012)$ resonance. We expect that present calculations can help us to better understand the nature of $Ω(2012)$ resonance.

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arXiv2023

Low-lying doubly heavy baryons: Regge relation and mass scaling

In framework of heavy-diquark$-$light-quark endowed with heavy-pair binding, we explore excited baryons $QQ^{\prime}q$ containing two heavy quarks ($QQ^{\prime}=cc,bb,bc$) by combining the method of Regge trajectory with the perturbative correction due to the heavy-pair interaction in baryons. Two Regge relations, one linear and the other nonlinear, are constructed semi-classically in the QCD string picture, and a mass scaling relation based on the heavy diquark-heavy antiquark symmetry are employed between the doubly heavy baryons and heavy mesons. We employ the ground-state mass estimates compatible with the observed doubly charmed baryon $Ξ_{cc}$ and spectra of the heavy quarkonia to determine the trajectory parameters and the binding energies of the heavy pair, and thereby compute the low-lying masses of the excited baryons $Ξ_{QQ^{\prime}}$ and $Ω_{QQ^{\prime}}$ up to 2S and 1P excitations of the light quark and heavy diquark. The level spacings of heavy diquark excitations are found to be smaller generally than that of the light-quark excitations, in according with the nature of adiabatic expansion between the heavy and light-quark dynamics.

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arXiv2022

Open charm and bottom meson-nucleon potentials à la nuclear force

We discuss the interaction of an open heavy meson ($\bar{D}$ and $\bar{D}^{\ast}$ for charm or $B$ and $B^{\ast}$ for bottom) and a nucleon ($N$) by considering the $π$, $σ$, $ρ$, and $ω$ exchange potentials. We construct a potential model by respecting chiral symmetry for light quarks and spin symmetry for heavy quarks. Model parameters are adjusted by referring the phenomenological nuclear (CD-Bonn) potentials reproducing the low-energy $NN$ scatterings. We show that the resulting interaction may accommodate $\bar{D}N$ and $BN$ bound states with quantum number $I(J^{P})=0(1/2^{-})$, and a $BN$ bound state with $I(J^{P})=1(1/2^{-})$. We find that, in the present potential model, the $σ$ exchange potential plays an important role.

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arXiv2022

Rich structure of the hidden-charm pentaquarks near threshold regions

The recent abundant observations of pentaquarks and tetraquarks by high-energy accelerator facilities indicate the realization of the conjecture by Gell-Mann and Zweig, and by De Rujula, Georgi and Glashow [1-3]. We construct a coupled-channel model for the hidden-charm pentaquarks with strangeness whose quark content is $udsc \bar c$, $P_{cs}$, described as $ Λ_c \bar{D}_s^{(*)}, Ξ_c^{('*)} \bar{D}^{(*)}$ molecules coupled to the five-quark states. These molecules are formed by the suitable cooperation of heavy quark and chiral symmetries. We reproduce the experimental mass and quantum numbers $J^P$ of $P_{cs}(4338)$ for which LHCb has just announced the discovery. We make other predictions for new $P_{cs}$ states as molecular states near threshold regions that can be studied by LHCb.

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arXiv2022

Decay properties of $N(1535)$ in the holographic QCD

We study one pion emission decay of the first excited state of the nucleon with negative parity $N(1535) \equiv N^*$ in the holographic model of QCD. The excited state is described as a vibrational mode along the extra $z$ direction in the five-dimensional space-time of the model. We have obtained an analytic formula for the axial coupling of $g_A^{NN^*}$. The off-diagonal axial coupling is obtained at the decaying pion momentum $|\boldsymbol{k}| = 448$ MeV as $g_A^{NN^*} \sim 0.32$, and hence a partial decay width $Γ_{N^* \to πN} \sim 30$ MeV, which is smaller than but reasonably compared to the experimental data.

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arXiv2022

Decays of Roper-like singly heavy baryons in a chiral model

We present a chiral model describing decays of the Roper-like $Λ_c(2765)$ and $Ξ_c(2970)$ as well as those of the heavy quark spin-doublet $\{Σ_c(2455),Σ_c(2520)\}$ and $\{Ξ_c',Ξ_c(2645)\}$, by focusing on chiral representations of diquarks inside the heavy baryons. Based on our chiral model together with the heavy quark spin symmetry, we derive a relation satisfied by axial charges of the heavy baryons that controls magnitude of their one pion (kaon) decays. Besides, it is shown that the large decay widths of the Roper-like $Λ_c(2765)$ and $Ξ_c(2970)$, which cannot be implemented by conventional non-relativistic quark models, are explained by reasonable values of the axial charges. In addition, we apply the chiral model to bottom baryons and predict decay widths of the undiscovered Roper-like $Ξ_b$. We expect that our present investigation leads to elucidation of dynamical properties of the excited heavy baryons from the viewpoint of chiral symmetry.

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arXiv2022

Substructure of Multiquark Hadrons (Snowmass 2021 White Paper)

In recent years there has been a rapidly growing body of experimental evidence for existence of exotic, multiquark hadrons, i.e. mesons which contain additional quarks, beyond the usual quark-antiquark pair and baryons which consist of more than three quarks. In all cases with robust evidence they contain at least one heavy quark Q=c or b, the majority including two heavy quarks. Two key theoretical questions have been triggered by these discoveries: (a) how are quarks organized inside these multiquark states -- as compact objects with all quarks within one confinement volume, interacting via color forces, perhaps with an important role played by diquarks, or as deuteron-like hadronic molecules, bound by light-meson exchange? (b) what other multiquark states should we expect? The two questions are tightly intertwined. Each of the interpretations provides a natural explanation of parts of the data, but neither explains all of the data. It is quite possible that both kinds of structures appear in Nature. It may also be the case that certain states are superpositions of the compact and molecular configurations. This Whitepaper brings together contributions from many leading practitioners in the field, representing a wide spectrum of theoretical interpretations. We discuss the importance of future experimental and phenomenological work, which will lead to better understandingof multiquark phenomena in QCD.

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arXiv2022

Electromagnetic transition amplitude for Roper resonance from holographic QCD

The Roper resonance, the first excited state of the nucleon, Is one of the best-established baryon resonances. Yet, its properties have not been consistently explained by effective models of QCD, such as the non-relativistic quark model. In this letter, we propose an alternative approach in the Sakai-Sugimoto model that is one of the holographic models of QCD. In particular, we analyze the helicity amplitude of the electromagnetic transitions at the leading of 't~Hooft coupling $1/λ$. The model incorporates baryon structure at short distance by non-linear mesons surrounded by meson clouds at long distance. We demonstrate that the recently observed data by CLAS are explained in the present approach.

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arXiv2022

Strong decays of multi-strangeness baryon resonances in the quark model

Decay properties of multi-strangeness $Ξ$ and $Ω$ baryon resonances are investigated within the constituent quark model by including relativistic corrections. The strong decay widths of various $Ξ$ and $Ω$ resonances are computed and tested for internal quark configurations to pin down their spin-parity ($J^P$) quantum numbers and internal structures. We found that the Roper-like resonances in the multi-strangeness sector have large decay widths bearing resemblances to their siblings in light and heavy baryon sectors. In addition, we obtained the decay ratio for the $Ω(2012)$ as $Γ{(Ω\to Ξ\bar{K} π)} / Γ{(Ω\to Ξ\bar{K})}=4.5\%$, which is consistent with the experimental data when $J^P=3/2^-$ is assigned. This observation holds the possibility that the $Ω(2012)$ could naturally be explained as a three-quark state in the quark model. The decays of other low-lying $Ξ$ and $Ω$ resonances are systematically analyzed, which would be useful to unveil the structure of these resonances in future experiments.

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arXiv2021

Extension of the J-PARC Hadron Experimental Facility: Third White Paper

The J-PARC Hadron Experimental Facility was constructed with an aim to explore the origin and evolution of matter in the universe through the experiments with intense particle beams. In the past decade, many results on particle and nuclear physics have been obtained at the present facility. To expand the physics programs to unexplored regions never achieved, the extension project of the Hadron Experimental Facility has been extensively discussed. This white paper presents the physics of the extension of the Hadron Experimental Facility for resolving the issues in the fields of the strangeness nuclear physics, hadron physics, and flavor physics.

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arXiv2021

Novel pentaquark picture for singly heavy baryons from chiral symmetry

We propose a new type of structure for singly heavy baryons of $Qqq\bar{q}q$ in addition to the conventional one of $Qqq$. Based on chiral symmetry of the light quarks, we show that the $Qqq\bar{q}q$ baryon offers a novel picture for heavy quark spin-singlet and flavor-antisymmetric baryons. By making use of the effective Lagrangian approach, we find $Λ_c(2765)$ and $Ξ_c(2967)$ are mostly $Qqq\bar{q}q$ while $Λ_c(2286)$ and $Ξ_c(2470)$ are mostly $Qqq$. The masses of negative-parity baryons are predicted. We also derive a sum rule and the extended Goldberger-Treiman relation that the masses of the baryons satisfy. Furthermore, a mass degeneracy of parity partners of the baryons with the restoration of chiral symmetry is discussed. These are the unique features that the conventional picture of radial excitation in the quark model does not accommodate. Our findings provide useful information not only for future experiments but also for future lattice simulations on diquarks.

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arXiv2021

Doubly Heavy Tetraquark Resonant States

Spectrum of the doubly heavy tetraquarks, $bb\bar q\bar q$, is studied in a constituent quark model. Four-body problem is solved in a variational method where the real scaling technique is used to identify resonant states above the fall-apart decay thresholds. In addition to the two bound states that were reported in the previous study we have found several narrow resonant states above the $BB^*$ and $B^*B^*$ thresholds. Their structures are studied and are interpreted by the quark dynamics. A narrow resonance with spin-parity $J^P=1^+$ is found to be a mixed state of a compact tetraquark and a $B^*B^*$ scattering state. This is driven by a strong color Coulombic attraction between the $bb$ quarks. Negative-parity excited resonances with $J^P=0^-$, $1^-$ and $2^-$ form a triplet under the heavy-quark spin symmetry. It turns out that they share a similar structure to the $λ$-mode of a singly heavy baryon as a result of the strongly attractive correlation for the doubly heavy diquark.

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arXiv2021

Classifying near-threshold enhancement using deep neural network

One of the main issues in hadron spectroscopy is to identify the origin of threshold or near-threshold enhancement. Prior to our study, there is no straightforward way of distinguishing even the lowest channel threshold-enhancement of the nucleon-nucleon system using only the cross-sections. The difficulty lies in the proximity of either a bound or virtual state pole to the threshold which creates an almost identical structure in the scattering region. Identifying the nature of the pole causing the enhancement falls under the general classification problem and supervised machine learning using a feed-forward neural network is known to excel in this task. In this study, we discuss the basic idea behind deep neural network and how it can be used to identify the nature of the pole causing the enhancement. The applicability of the trained network can be explored by using an exact separable potential model to generate a validation dataset. We find that within some acceptable range of the cut-off parameter, the neural network gives high accuracy of inference. The result also reveals the important role played by the background singularities in the training dataset. Finally, we apply the method to nucleon-nucleon scattering data and show that the network was able to give the correct nature of pole, i.e. virtual pole for ${}^1S_0$ partial cross-section and bound state pole for ${}^3S_0$.

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arXiv2021

Unveiling the pole structure of S-matrix using deep learning

Particle scattering is a powerful tool to unveil the nature of various subatomic phenomena. The key quantity is the scattering amplitude whose analytic structure carries the information of the quantum states. In this work, we demonstrate our first step attempt to extract the pole configuration of inelastic scatterings using the deep learning method. Among various problems, motivated by the recent new hadron phenomena, we develop a curriculum learning method of deep neural network to analyze coupled channel scattering problems. We show how effectively the method works to extract the pole configuration associated with resonances in the $πN$ scatterings.

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